Combination toll and local connector switch used in telephone systems



Aug. 16, 1949. R. TAYLOR ET AL 2,479,276

I COMBINATION TOLL AND LOCAL CONNECTOR SWITCH USED IN TELEPHONE SYSTEMS Filed April 26, 1945 5 Sheets-Sheet 1 I Y NR2 i 0P3 W54 +.1TK 7 s PITK mvENToRs REGINALD TAYLOR GEORGE THOMAS BAKER ATTORNEY Aug. 16, 1949. R. TAYLOR EI' AL 2,179,276

COMBINATION TOLL AND LOCAL CONNECTOR SWITCH USED IN TELEPHONE SYSTEMS Filed April 26, 1945 3 Sheets-Sheet 2 1O DD3 F17. E DD4 F5 fl NZ H 2 B3 DD2 INVENTORS REGINALD TAYLOR GEORGE THOMAS BAKER ATTORNEY Aug. 16, 1949. R. TAYLOR ET AL 2,479,276

COMBINATION TOLL AND LOCAL CONNECTOR SWITCH USED IN TELEPHONE SYSTEMS Filed April 26, 1945 5 Sheets-Sheet 3 INVENTORS REGINALD TAYLOR GEORGE THOMAS BAKER ATTORNEY Patented Aug. 16, 1949 STATES PATENT GQMBINATIQN"; TOL NESTOR, JSWITGHC PHONE SlS- -R'egi'nald Taylor and George y England; assignorsto Automatic L AND: mean 610m .vUSEDx .TELEe Tho as Baker;

.sElectric Laboratories, Inc., Chicago; IIl' a cor-w aeration oiiDela-wa ean icat qn Am se 1945,stamens];

j 'IirGreat Britain J unex 15,1944:

I Present-inventions relates: to automatic switches: at the-type :usedfi hr telephones. orlike systems amidst-moreparticularlyconcerned: with toi a wanted par-tys: line:

thesinventiom is to: :provide -.an: improvedswitchcircuit:-; givingsadditinnalifacilities and particu1arly enablingeamoperaxtofito vcontrol the setting up:

of.:1cngtdistance- Qonneotionsrwhen; this; involvescutting imorr cinch-subsequently breakingndown: em

existing; cmmectiom.

Accordinsgto. one feat'unetof theainventiom in a= finaizselectorzswitch amtangedgtmbeeaccessible to both: epetators, ands suiismzibers; over:- 'diflerent means. QfiEGCBSS,-I equipment responsive: toz izurea ofzthezswitela-c' oven one of access but not o v erthe otheeziszarrazngeciz tm effect: circuit: changes.- suchrthat am opera-tor ent transmittedsfromzwhich? it is: atherwiseaunresponsiyezz when; the switch isseizedr by:- St responsible; to CDIItIIOIi. signals:

thee; operator's; position to Aecerdingsto:anothemfeature:0t thesinvention,

in: as fin-a1: selector: switch":

arranged "tozpermit an operatorqtmcufiimoni and "breaks down 1 anexistzing, connectionyif'the switcm is positionedon to a busy linQ-a signak suitablez-forfiashing a1- super visorywlamp isetransmittedthaekefrom: therswitch while in: addition: artonesignalais or: is"not sent backr aocording to' tl,1e'.-natureaof-ithe existing; conr30 further featurerofr-the:inventiomis that in. a:

nection.

final;- selectonxswitehe acrangedi to: be accessible to both: operators: and subscribers: over: different meansz of access;..if-=.theswitchi is positionedonto 1 art-busy line-.ihyr: a: subscriber he receives thezsam'e' long distance or: a: local/connection: while. if the switclmis positioned on -to -asbusy line by t an operator she receives a; different busysigna'l according: to the naturemfi'theexisting connection.

The invention will beibetter understood from' thelfollowing; clescriptiomof: onez-methodf of; carrying-itcinto effectswhiehshouldubetakeniin conjunctionmwith' theeaccompanying drawings: comprising Figs. 1', 23andc3. a :Flthesezwhen placed: side-- by'sidej -iimord-er withmigi lz'omthedeftLshow the.-

grou pst-ofr-fmm' 2: to l'fl lines butz'itzwill I be 1 understoodth-at -the main features of the invention are also applicable tmregular: finaI-selectors and to P? B: ifi flnall selectors arranged tocater for groups-greater than 1 0i- Moreover the -features of the invention are n=ot '-limitedt'o final selectors provided with two sets of wipers The 'switemin questibmifs oi the well-known m the; ve 59 i lo e e in i c seizeglj The switch moreover ubscribers anrl operators-- vertical; anrilrotary typearranged: to have soi l dsrestanelila fi l 1 lthwt a separate release magnetiarrcl ,proylqegif' with two sets of wipers the selectiqn ,of; which-is dependent selector over which he sw t is accessible' to bot m ha t ere are burrfiifi iit me f accesso resn e i j esnq i ei iw s r be sei over twodifierentieyels and operajtoP-seizureover two pliiierentlevels;

into-usebya subscriber overwselectorleveI such that the normal set of wipers -1"s -us e"d, thatis tosay overt-he line ponductorsand? 1 When this occurs-relay it is operated orepthe line; and at contacts 'A'lf completes a circuit fcr rel-ayB by way; of contacts C1 and- N4, rectifier MRE and" resistor; YB; Rectifier MRB -is included in: this circuit in accord'ance with knowmpractlce in order to prevent thelowwesistance-battery'connectio'n havinga slugging effect on the operating magnets during subsequeneim puls-ing: Bela-y B t on operating, ati-eont'actfs Bheartiis theincomihg P conductor;- at contacts J32 completes a circuit for theright-hand winding ofnrelaysCz in; serieswithresistor' at contactsBii, Fig; 2 prepares a; circuit for-relay at-contacts B42 prepares a circuit-for re1ay-E and?- ar shunttior relay; 0; at.-

contacts;B5-completes arlockingzcircuit:for. itself;

and at'-- eontacts-., B6 -opensiapoiniain. the .release;

circuitand prepares aecirculation-relay HSz v Relay C operates at this time andtata contacts? C I,.

Fig. 2', opens a point i-mthe circuiieofi relay H;.and prepares for the: subsequeninmeteriirgr operation;

at contacts Cz changessover thecircuitt-oi relay E,

at contacts -3 prepares a=sloolsing circuitziorrelay HS, at contacts C4 providesa ant. additional shnn-t for thedeft han'dwindingiof reIay'QP; at contacts C5 prepares axlocking circuit-for relay" G, at-contacts:cli elosesapoint ir'ntheim-pulsing circuit and at contacts fll opens a point-in: the circuit for guarding the switch -during: release conditions.

No further- -operations take-place until-the succeeding -di'g it is: transmitter};- whereupon" relay A deenergi'ses-in: accordance with -the ii'npulses and on; each de -energisation -completes a circuit from earth overcontacts l35, AH and G6; left-hand low-resistance winding; of f relay cg contacts E6" and= NR I; verticaf'magnet VM to battery. The

N2 a locking circuit is prepared for relays WS and OP, at contacts N3 the right-hand winding of relay C is short-circuited and at contacts N4 the initial circuit of relay B is opened and a guarding circuit is prepared. Relay C is rendered slow by the short-circuiting of its righthand winding and remains energised as long as impulses are transmitted through its left-hand winding. At the end of the train it de-energises and thereupon at contacts C2 completes a circuit for relay E in series with the vertical magnet VM which is not now operative. Relay E at contacts El prepares a locking circuit for itself, at contacts E2 removes the short-circuit from relay C which therefore again energises, at contacts E3 removes the short-circuit from the lefthand winding of relay WS, at contacts E4, Fig. 2, opens a point in the circuit of relays G and J, at contacts E5 closes a point in the booster battery metering circuit, at contacts E6 changes over the impulsing circuit to the rotary magnet RM, at contacts E1 removes one of the multiple earths opens a pointin the release circuit.

The switch is now ready for the final digit and when this is received, relay A responds as before. Corresponding impulses are therefore transmitted through the left-hand winding of relay C and over contacts E6, NI and H8 to the rotary magnet RM which accordingly advances the wipers into engagement with the desired line. On the first rotary step the rotary off-normal contacts are operated, thereupon at contacts NRI opening the initial circuit of relay E, at contacts NR2 removing one of the shunts round the left-hand winding of relay OP, at contacts NR3 again shortcircuiting relay C and at contacts NR4 short-circuiting the left-hand winding of relay WS. Accordingly at the end of the train of impulses relay C again releases and at contacts Cl provides an operating earth for relay H and at contacts C2 opens the locking circuit of relay E which commences to release slowly.

If the line is busy, the Pl wiper will encounter earth and relay H will be short-circuited and thereforeunable to operate. Hence, on the release of relay E a circuit is completed from earth over contacts B4, N3, NR3, HSG, E4, H2 and CNS to battery through the lower winding of relay G. Relay G accordingly operates and at contacts Gl connects up flash battery from common lead III, which will be ineffective in the present case since a subscriber is calling, at contacts G2, Fig. 1, opens a point in the release circuit, at contacts G3 removes the normal earth connection from the upper winding of relay A so that the flash battery may be effective, at contacts G4 prepares a circuit for relay CN and at contacts G5 connects up busy tone which extends to the middle winding of relay A by way of common lead [8 and contactsOPt and HS3. The subscriber accordingly hears busy tone and realizes that he cannot obtain his connection.

When he subsequently replaces his receiver, relay A de-ener-gises and at contacts Al shortcircuits relay B which accordingly releases after its slow period. Relay B brings down relays C and G and a release circuit for the switch is then completed over common lead l6 which extends to earth by way of delayed alarm equipment, contacts B6, RMC, E8, CNS, G2, NI and H8, rotary magnet RM to battery. The rotary magnet therefor advances the wipers to the 12th position after which they fall and rotate back to normal underneath the bank by spring tension. The rotary from the P conductor andat contacts E8' MIA at this stage serves magnet circuit is opened at contacts NI when normal position is reached. During the release operation, guarding ductor by way of contacts Cl and N4.

If the wanted party is idle, however, wiper PL will encounter battery and this will be extended over contacts W83, BD-i, right-hand winding of relay H, contacts B3, left-hand winding of relay H, contacts Cl and CNZ, rectifier MRA to earth. It may be mentioned that the purpose of the rectifier MRA is to prevent the operation of relay H in case the line is busy but wiper Pl picks up booster battery because a metering operation is taking place. Relay H on operating, at contacts HI and H5 connects up the line wipers, at contacts H2 prepares a circuit for relay J, at contacts H3 and H4 connects the back bridge relay D to the speaking conductors, at contacts H6 short-circuits its high resistance left-hand winding to busy the line, at contacts H1 prepares a locking circuit for relay F and at contacts H8 opens a point in the release circuit, The circuit of relay J is completed as soon as relay E releases and thereupon at contacts J l is connects up ringing current by way of common lead l9 and the right hand winding of ring trip relay F to the negative conductor, the ringing return being by way of resistor YA and common lead IT, at contacts J2 prepares the metering circuit, at contacts J3 connects ringing tone from common lead H to the middle winding of relay A and at contacts J4 prepares a circuit for relay BD.

The wanted party is now rung in the usual manner and when he replies, relay F operates and thereupon at contacts Fl prepares the circuit of the supervisory lamp LP which extends to battery over delayed alarm equipment by way of common lead l5, at contacts F2 and F3 disconnects the ringing circuit and switches the speaking leads through, at contacts Ft removes the short-circuit from its left-hand winding thereby providing an effective locking circuit in series with resistor YC, at contacts F5 opens the ringing tone circuit and at contacts F5 prepares an alternative locking circuit for relays WS and OP and prevents relay C being short-circuited on the subsequent re-operation of relay E. When the speaking conductors are switched through, relay D is operated over the called partys loop and at contacts D! brings up its relief relay DD. This relay at contacts DDI completes a circuit for relay E, at contacts DD2 opens a point in a shortcircuit round the righ hand winding of relay H, at contacts DD3 and DD4 reverses the connections of relay A to the incoming line to give the usual supervision and at contacts DD5 opens a point in the circuit of the supervisory lamp LP. The operation of relay E at this time at contacts E5 connects booster battery to the P conductor to effect metering and also at contacts E4 opens the circuit of relay J. During the release time of relay J therefore, the booster battery metering condition is maintained and the call is accordingly charged against the calling party. Rectifier to prevent release of the preceding switches while the metering contacts are changing over. The connection has now been fully set up and'the parties may converse.

The circuit as shown is arranged for last party release. Assuming that the called party hangs up first, relay D then releases and brings down relay DD. Thereupon the current flow over the incoming conductors is reversed back to normal and at contacts DD5 a circuit is prepared for the supervisory lamp LP whichis thus efiective after earth is applied to the P con-- .7 circuited ensures that the signalling operations proper to an operator cannot be performed by a subscriber either due to a fault on his line or with malicious intent. Moreover, the fact that the windings of this relay are not included in the line circuit during impulsing improves the response of relay A. The immediate operation of relay F ensures that ringing shall not be started automatically when connection is made with the wanted line and this feature is desirable to cater for the case in which the operator is completing a delayed call and does not wish to signal the called party until she has the calling party back on the line.

Assuming that the wanted party is idle, relay I-I operates in normal manner and brings up relay J whereupon a circuit is completed from earth, contacts H6, low resistance winding of relay H, contacts J 4 and P1, winding of relay B1) to battery. Relay BD thereupon at contacts BDI prepares a circuit for short-circuiting the lefthand winding of relay F, at contacts BD2 connects the low resistance lower Winding of retard TB to the P conductor for guarding and holding purposes, at contacts B133 extends busy tone from common lead l2 over contacts H83 and OPE and capacitor QD to the P conductor and at contacts BD4 disconnects relay H from this conductor and connects it in series with relay BD. The wanted line has therefore been seized and marked busy but no signalling has yet taken place. When the operator subsequently wishes to complete the connection, she throws her ringing key thereby earthing the line and thus unbalancing relay DF which accordingly operates and at contacts DFI extends earth over contacts G4 and CN3 to short-circuit relay 3?. Relay F then deenergizes and connects up ringing current in the usual manner and owing to the operation of contacts BDI, relay F remains shortcircuited after the operator releases the ringing key and is only re-operated .over its right-hand winding when the wanted party replies. Relays D and DD are then energised but owing to the opening of contacts 0P8 no circuit is completed for relay E. and metering does not take place. In these circumstances relay J remains operated for the remainder of the connection.

If the operator finds the wanted line busy, earth will be picked up by the Pl wiper so that relay H cannot operate and relay l3 is energised by Way of its lower winding in the usual manner on the release of relay E. Thereupon the operator receives a busy flash signal by the intermittent connection of earth and battery to common lead is but if the subscriber is busy in a local connection she does not receive tone since relay BI) is not yet operated and the normal tone connection over lead 18 has been cut oil at contacts 0P6. It will be noted that during the flash periods, that is to say while battery is connected to lead ll], relay A is maintained operated over its middle winding in series with the two windings of retard TB. The operator, being thus notified that a local connection is concerned, may decide to cut in on the connection in which case she again operates her ringing key to earth the line and energises relay DF. In these circumstances a circuit is completed over contacts DFl, G4 and HS8 and. the right-hand winding of relay CN to battery by way of resistor YD. Relay CN thereupon at contacts CN! and 0N4 connects the speaking leads through to the line Wipers, at contacts CN2 provides an operating earth for relay H, at contacts CN3 prepares a circuit for relay BD, at contacts CNS opens a point in the rotary magnet circuit and at contacts CNS opens the circuit of relay G and locks up over its left-hand winding. Relay G holds in series with the right-hand winding of relay ON by way .of resistor YF and thus does not fall away until the ringing key is released. The operator may now converse with the wanted party and may if necessary break down the existing connection by further operation of the ringing key. In this case contacts DFI extend earth over contacts G4 and CN3 to operate relay BD. Relay BD thereupon by connecting the low resistance lower winding of the retard TB to the P conductor breaks down the existing connection. It will be understood that if the wanted party is the calling party in the existing connection this low resistance earth shunts down the cut-on relay in his line circuit, which may be .of the type disclosed in our application Serial No. 567,551, filed December 11, 1944, now Patent No. 2,424,519 dated July 22, 1947, while if he is the called party, it shunts down the H relay in the final selector. When the key is released, relay I-I operates in series with relay BD and releases relay CN. Relay J now operates and the operator may initiate ringing by a further manipulation of her key as previously described.

If, on the other hand, the subscriber is engaged in a long distance connection, tOne from common lead l2 applied to the P conductor in the existing connection will be extended over capacitor QD and contacts 0P6, HS3 and G5 to the middle winding of relay A and the operator will therefore receive both busy flash and tone and will thus know that it is not desirable for her to disturb the existing connection.

. It will be appreciated that if the operator seizes the switch by way of the other means of access, that is to say over the leads 2TK and +2TK, relay WS will be operated between the two digits and will connect up the second set of wipers. All the other operations take place as just described.

It will be understood that if desired the tones from the two sources, that is to say over leads l2 and I8 respectively might be of a different amplitude and/or difierent frequency or with a different code of interruption. This would be primarily for the benefit of a maintenance man or monitoring operation, since the regular operator always receives tone from one source only, namely over lead I2, while a calling subscriber always receives tone from the other source only, namely over lead l8.

It may be mentioned that-if a P. B. X group is concerned it may be the practice for the operator to connect herself to the last line of the group by dialling the appropriate number on the assumption that this line is most likely to be free. If, however, she finds that a trunk connection is involved thereover, she will release the connection which she has set up and dial an intermediate line in the group in the hope of finding a line engaged in a local connection which she can then break down.

According to the invention, therefore, an improved final selector has been provided which without sacrificing reliability of operation or involving an appreciable increase in the amount of equipment required gives additional facilities which in some circumstances may be of considerable advantage.

We claim:

1. In a telephone system, a connector switch,

a path accessible to an operator over which the switch may be seized, a path accessible to subscribers over which the switch maybe seized, means in the switch controllable by said operator for controlling the switch, means normally short-circuitin-g said first means thereby rendering said first means normally inoperative, said first means remaining short-circuited when the switch is seized and operated by a subscriber over said second path, and means in said first path operated after the switch has been seized over that path for causing the disablement of said short-circuiting means thereby to render, said first means effective and subject to control by said operator.

2. A telephone system as claimed in claim 1 in which said means in said first path comprises a relay which is included only momentarily in said first path.

3. In a telephone system, a plurality of lines certain of which may be busy in toll calls or in local calls, a switch having access to said busy lines, said switch accessible to an operator and operable to seize one of said busy lines, means in said switch responsive to the seizure of one of said busy lines under control of said operator for giving said operator a busy flash signal whether said seized line is busy in a toll call or in a local call, and means responsive to said seizure of said one busy line for returning a tone signal to said operator only if said seized line is busy in a toll call.

4. In a telephone system, a combination toll and local connector operable by an operator over one path and by local subscribers over another path, said paths having talking conductors, a relay momentarily included in one of said talking conductors of said one path after said connector has been operated by said operator over said one path, means for operating said relay responsive to said momentary inclusion of said relay in said one talking conductor of said one path, said relay not included in a talking conductor of said other path when said connector is operated by a local subscriber over said other path.

5. In a telephone system, a connector switch, local lines accessible to said switch, difierent paths over which said switch may be seized by a local line or an operator, a relay in said switch normally short-circuited, means in said switch operated when said switch is seized and operated by said local line over one of said paths for selooting and signalling a called local line, another relay in said switch, means in said switch for causing the momentary inclusion of said other relay in said other path when said switch is seized and operated over said other path, said other relay operated responsive to said inclusion to remove said short-circuit from said first relay, and means controlled by said first relay when said short-circuit is removed for controlling the selecting and signalling operations of said switch in a different manner.

6. In a telephone system, a combination local and toll connector switch operable by local stations over one path and by an operator over another path, said other path having talking conductors, means in said connector for automatical- 1y signalling a called local station, said means efiective when said switch is operated by one of said local stations over said one path, a relay momentarily included in one of said talking conductors of said other path when said switch is operated by said operator over said other path, means for operating said relay responsive to said tion of said relay causing the disablement of said first means.

7. In a telephone system, a plurality of lines certain of which are busy in telephone connections, a switch having operating conductors and a line relay connected to said conductors, said busy lines accessible to said switch, said line relay of said switch operable by an operator over said conductors for causing said switch to seize one of said lines, an auxiliary holding circuit, another relay in said switch, means in said switch responsive to the operation of said switch by said operator for momentarily including said other relay in one of said conductors, said other'relay operated responsive to its momentary inclusion in said one conductor to connect said auxiliary holding circuit to said operated line relay, means in said switch responsive to the seizure of one of said busy lines for giving said operator an interrupted signal to indicate to said operator that said seized line is busy in a telephone connection, said interrupted signal intermittently dis abling said first connection of said line relay, said auxiliary holding circuit maintaining said line relay operated during the intermittent periods said interrupted signal disables said first connection of said line relay.

8. In a telephone system, a switch operable over a path having talking conductors, a relay in said switch normally short-circuited, means in said switch responsive to the operation of said switch over said path for momentarily removing said short-circuit from said relay thereby to momentarily include said relay in one of said talking conductors, said relay operating in response to said momentary inclusion in said one talking conductor, and means in said switch for retaining said relay in said operated position.

9. In a telephone system, a switch operable over a path having talking conductors, a relay in said switch having two windings, means in said switch short-circuiting one of said windings of said relay, means in said switch responsive to the operation of said switch over said path for disabling said short-circuiting means thereby to include said one winding of said relay in one of said talking conductors, means responsive to said inclusion of said one winding in said one talking conductor for causing said relay to operate, means in saidswitch including said other winding of said relay for causing said relay to lock in said operated position, and means in said switch for thereafter short-circuiting said one winding of said relay.

REGINALD TAYLOR. GEORGE THOMAS BAKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Great Britain Oct. 12, 1933 

